The present invention relates to a turbomachine stage, in particular a turbine or compressor stage of a gas turbine, having a, in particular conical, housing, in which a rotor blade arrangement having a plurality of rotor blades is disposed, which comprises an outer shroud having at least one radial sealing flange, and a method for detecting a sealing gap of such a turbomachine stage.
The sealing gap between the housing and the outer shroud can be reduced by one or more radial sealing flanges disposed successively in the axial direction. In the process, in particular because of different operating conditions, it is possible for rubbing to occur between the sealing flange and the housing, and subsequently for an abrasion to occur on the sealing flange and/or a worn area in the housing thereby altering the sealing gap. Knowledge of the actual sealing gap can be advantageous, in particular for adjusting the operation of the turbomachine thereto and/or for carrying out or planning maintenance.
One object of an embodiment of the present invention is to improve the maintenance and/or the operation of a turbomachine stage.
A turbomachine stage according to one aspect of the present invention can be in particular a turbine or compressor stage of a gas turbine, preferably of an aircraft engine.
It comprises a rotor blade arrangement having a plurality of adjacent rotor blades in the circumferential direction, which can be configured to be detachable or fixed, in particular integral, with a rotor of the turbomachine. The rotor blade arrangement is disposed in a housing, which, in one embodiment, can converge or diverge in the direction of flow, at least in the region of the rotor blade arrangement, and which for a more compact representation is designated here in general as a conical housing. Similarly, the housing can have, at least in the region of the rotor blade arrangement, an at least substantially constant cross section in the direction of flow, which is designated here accordingly as a cylindrical housing.
The rotor blade arrangement comprises an outer shroud, which can be formed of a plurality of outer shroud sections, each of which can be connected to one or more rotor blades. In one embodiment, the outer shroud can converge or diverge in the direction of flow or can comprise an at least substantially constant outer circumference, which is designated here accordingly as a conical or cylindrical outer shroud.
Disposed radially outside on the outer shroud are one or a plurality of radial sealing flanges spaced apart from each other in the axial or flow direction, which preferably extend rib-like radially outwardly and in the circumferential direction. Such radial sealing flanges are also designated as sealing fin(s) for short in the following.
According to one aspect of the present invention, the single sealing flange, in the case of a plurality of sealing flanges spaced apart from each other in the axial direction of one or a plurality of, in particular all, sealing flanges respectively comprises a recess arrangement having one or a plurality of radial recesses. A plurality of radial recesses can be distributed equidistantly or asymmetrically over the circumference. In one embodiment, the recess arrangement comprises precisely two, three or four recesses. In one embodiment, a recess can comprise two opposing flanks, which, in a further development, extend, at least substantially, in the radial direction and/or merge into an adjacent, preferably cylinder ring-shaped, outer circumference of the sealing flange, preferably into a rounding. Extending between the flanges in a further development is a recess base, which in one embodiment can have, at least substantially, a cylinder ring-shaped circumferential surface. Consequently, in one embodiment a recess can be configured to be U-shaped in particular.
A radial projection is disposed in the recess. It can extend radially outwardly in particular from the recess base and in a further development can comprise, at least substantially, a cylinder ring-shaped circumferential surface. The radial projection can be disposed, as viewed in the circumferential direction, in particular centrically in the recess, but similarly also eccentrically. In one embodiment, the recess with the projection disposed therein is configured symmetrically, which in the case of rotations in the opposite direction can produce advantageously homogenous signals. Similarly, the recess with the projection disposed therein can also be configured asymmetrically in order to produce advantageously different signals in the case of rotations in the opposite direction.
Disposed on the housing is a sensor arrangement having one or a plurality of capacitive sensors or probes for detecting a radial distance from a circumferential surface of the sealing flange. A plurality of sensors can be distributed equidistantly or asymmetrically over the circumference. In one embodiment, the sensor arrangement comprises precisely two, four or six sensors. A capacitive sensor for detecting a radial distance from a circumferential surface of the sealing flange is understood here in particular as a means that supplies a signal, which is a function of a radial distance of the sensor from the circumferential surface, preferably non-linear. Designated as a circumferential surface here is in particular a surface of a sealing flange, of a recess or of a projection, which extends in the circumferential and axial direction, i.e., the upper side of the sealing flange, of the recess or of the projection as viewed from the radial outside.
When a recess travels over a sensor the radial distance changes: it increases to begin with as soon as the sensor detects the recess base. Then the radial distance decreases when the sensor detects the projection. Then it increases again as soon as the sensor detects the recess base on the opposite side of the projection in the circumferential direction. Then the radial distance decreases again to the initial value when the sensor detects the circumferential surface of the sealing flange next to the recess. Therefore, in one embodiment, when a recess rotates past a sensor, a generally W-like signal progression with four alternating, opposite-direction signal swings is produced. A signal swing is designated here in particular as a, substantially step-shaped, increase or decrease of the signal or signal value of the sensor.
According to one aspect of the present invention, at least one signal swing of the sensor arrangement is detected as a result of a detection of at least one recess of the recess arrangement and of the projection in the recess by means of at least one sensor of the sensor arrangement. The subsequent detection or analysis explained based on a recess and one or two sensors can be carried out in the same manner for a plurality of recesses and/or sensors, wherein then, in one embodiment, the detection results can be compared with one another, in particular can be averaged.
In one embodiment, the signal swing, which is yielded as a result of the change in distance between the recess base and the projection and/or between the projection and the recess base, is allocated to a radial distance of the rotor blade arrangement based on a previous calibration: in the case of a capacitive sensor, the capacity of a capacitor detected directly or indirectly changes as a result of the change in the effective circumferential surface of the recess base or the projection. The change or signal swing is different in the case of different radial distances of the sealing flange from the sensor or the housing, on which it is disposed. Correspondingly, the signal swing can be allocated to a specific radial distance, wherein in a previous calibration, specific signal swings were allocated accordingly to specific radial distances. The allocation of a detected signal swing to a radial distance based on a previous calibration can be carried out in particular by, preferably linear, interpolation or extrapolation between value pairs of the calibration.
In one embodiment, the sensor arrangement has at least two sensors, the detection surfaces of which enclose, with an axis of rotation of the turbomachine stage, different angles, in particular in opposite directions, preferably at least substantially of equal amounts. In terms of amount, the angles are preferably greater than 5°, in particular greater than 10°. In addition or as an alternative, in one embodiment they are less than 25°, in particular less than 20° in terms of amount. In one embodiment, the angles are, at least substantially, equal to ±15°.
A sensor comprises a detection area in the circumferential direction. The successive detection areas in the axial direction together form one detection area within the meaning of the present invention. A sensor comprises in particular a detection area, which encloses an angle with the axis of rotation, when the sensor detects displaced recesses or projections in the axial direction correspondingly earlier or later. The greater the amount of the angle, the earlier or later the sensor detects two displaced or aligned recesses in the axial direction. For example, if a sensor comprises a rectangular sensor surface facing the sealing flange, the main axis of which encloses an angle with the axis of rotation of the turbomachine stage, then the detection area also correspondingly encloses this angle with the axis of rotation.
Because of these detection surfaces that are inclined with respect to the axis of rotation of the turbomachine, it is possible in one embodiment for an axial position of the rotor blade arrangement to be detected. To this end, in one embodiment, first a signal swing of the sensor arrangement is detected as a result of a detection of a recess of the recess arrangement and of the projection in the recess by means of a sensor of the sensor arrangement. By further rotating the rotor towards a further sensor, a further signal swing of the sensor arrangement is detected as a result of a detection of this recess and of the projection in this recess by means of a further sensor of the sensor arrangement. The distance of these signal swings, in particular the time-related distance or rotation angle distance, can then be allocated based on a previous calibration to an axial position of the rotor blade arrangement. If the detection surfaces of two sensors converge in the axial direction, then the distance of the signal swings decreases the farther the sealing flange is displaced in the axial direction. Conversely, the distance increases in the case of detection surfaces diverging in the axial direction or a displacement against the axial direction.
Just as explained in the foregoing relating to the signal between the recess base and the projection or the projection and the recess base, a signal swing is also produced when a recess enters or exits the detection surface of a sensor. In one embodiment of the present invention, the sensor is used to detect an abrasion of the sealing flange: the greater the abrasion, the smaller the signal swing. Accordingly, in one embodiment, at least one signal swing of the sensor arrangement can be detected as a result of a detection of a recess of the recess arrangement and of a circumferential surface of the sealing flange adjacent to the recess, in particular upstream or downstream in the rotational direction, by means of a sensor of the sensor arrangement and the signal swing can be allocated to an abrasion of the sealing flange based on a previous calibration.
The sealing gap between the sealing flange and the housing, in particular an abradable lining of the housing, can, along with the radial distance of the sealing flange from a housing-mounted sensor and a possible abrasion of the sealing flange, also be a function of a worn area on the housing and/or the axial position of the sealing flange. Accordingly, in one embodiment of the present invention, a worn area of the housing opposite from the sealing flange, in particular of an abradable lining of the housing opposite from the sealing flange, can be detected, in particular periodically. This can be taken into account in the detection of the sealing gap, in particular added to a detected radial distance and/or to an abrasion of the sealing flange.
As explained in the foregoing, the signal swings or the distances thereof can be allocated to radial distances or axial positions through a, preferably two-dimensional, calibration. Correspondingly, in one embodiment of the present invention, to begin with, an axial position of a sealing flange is determined from the distances between the signal swings, which successively detect the same recess by means of sensors having detection surfaces inclined in opposite directions, and subsequently from the signal swings between the recess base and the projection or the adjacent, non-recessed circumferential surface of the sealing flange based on the two-dimensional calibration of the radial distance or abrasion of the sealing flange. In a further development, an actual sealing gap can be determined from this along with the likewise detected worn area.
In one embodiment of the present invention, a circumferential surface of the radial projection is lowered radially in the recess. Through this, an abrasion of the remaining circumferential surface of the sealing flange surrounding the recess also does not change the signal swing between the recess base and the projection.
A recess can be disposed completely in an outer shroud section. Similarly, a recess, in particular the projection, can be configured in common by two adjacent outer shroud sections or the recess, in particular the projection, can extend over the contact surface of two adjacent rotor blades. In the process, the recess, in particular the projection can be symmetrically distributed to two adjacent outer shroud sections or extend symmetrically to the contact surface.
In one embodiment, the sealing flange of one or two adjacent outer shroud sections is lowered radially with respect to the sealing flange of the further outer shroud sections following it or them so that the recess extends over one or both complete outer shroud sections. In this way, it is especially simple to constitute a recess with a radial projection. The radial projection can be disposed on the facing contact surfaces of these adjacent outer shroud sections.
In one embodiment, the turbomachine stage comprises a processing means, which is equipped to carry out the method described here. A means within the meaning of the present invention can be configured in terms of hardware and/or software, in particular a digital processing unit, in particular a microprocessor unit (CPU), preferably connected in terms of data or signals to a storage system and/or bus system, and/or one or a plurality of programs or program modules. The CPU can be configured to execute commands, which are implemented as a program stored in a storage system, detect input signals from a data bus and/or emit output signals to a data bus. A storage system can comprise one or a plurality of, in particular different, storage media, in particular optical, magnetic, solid-state and/or other non-volatile media. The program can be constructed in such a way that it is able to embody or execute the method described here so that the CPU can execute the steps of such a method and thus detect a sealing gap in particular.
Additional advantageous further developments of the present invention are disclosed in the following description of preferred embodiments. The drawings are partially schematized.